Readability is a crucial presentation attribute that web summarization algorithms consider while generating a querybaised web summary. Readability quality also forms an important component in real-time monitoring of commercial search-engine results since readability of web summaries impacts clickthrough behavior, as shown in recent studies, and thus impacts user satisfaction and advertising revenue. The standard approach to computing the readability is to first collect a corpus of random queries and their corresponding search result summaries, and then each summary is then judged by a human for its readabilty quality. An average readability score is then reported. This process is time consuming and expensive. Besides, the manual evaluation process can not be used in the real-time summary generation process. In this paper we propose a machine learning approach to the problem. We use the corpus as described above and extract summary features that we think may characterize readability. ...